This invention relates to foot prostheses in general, and specifically to a prosthetic foot characterized by a unitary foot and heel construction, and/or an auxiliary ankle construction which permits the flexibility of the prosthesis to be selectively determined and easily changed. The invention also includes an improved coupling for attaching said foot prosthesis to an auxiliary pylon tube.
The prior art is replete with various types of mechanical devices purporting to solve the foot prosthesis problem. Typical of early devices if Lange U.S. Pat. No. 2,075,583, which incorporates a rubber form mounted in operative relationship with a rigid metallic core. Exemplary of the latest developments in the field is Poggi U.S. Pat. No. 4,645,509, which teaches a prosthetic foot incorporating a monolithic keel or beam of relatively massive proportions intended to react to the load of an amputee""s body during walking, running, jumping, and the like and to release the resultant stored energy to create foot lift and thrust complementing the amputee""s natural stride.
However, each of the prior art devices has significant deficiencies; specifically, the component parts of the prosthesis, as in Lange, are too heavy and too rigid or, as in Poggi, are too massive and monolithic to respond properly to the nuances of stress-response gradients characteristic of the human foot.
One of the primary factors which has inhibited the creation of a truly successful prosthetic foot has been the fixation of the prior art with the duplication of the structural aspects of the skeletal and muscular components of an actual human foot. In many instances, as exemplified by Poggi ""509, mentioned hereinabove, even the toes of the foot are attempted to be duplicated by providing simulacra thereof. It is this fixation upon the mechanical elements of the human foot which has restricted the art to an attempt to duplicate the human foot components, a tendency which is particularly exemplified in Gajdos U.S. Pat. No. 3,335,428.
My copending application Ser. No. 07/293,824 discloses certain concepts relating to a prosthetic foot characterized by a forefoot portion and a heel portion which may be permanently or demountably associated with each other whereby both the forefoot portion and the heel portion can be readily exchanged with corresponding constructed heel and forefoot portions. This exchangeability permits size adjustment or accommodation of different spring rates to suit the size of foot of the amputee or the stride and weight of the amputee, yielding an almost infinite range of combinations of spring rate and size to the amputee, and allowing a natural stride and resilience of gait which has not been obtainable by prior art prosthetic devices. Other than my present invention and my copending application, I am unaware of any prosthetic foot device incorporating such demountably attached forefoot and heel portions, and providing such ease and range of adjustability.
It is, therefore, an object of my invention to provide a foot prosthesis which is characterized by a foot portion and an ankle portion which may be permanently or demountably associated with each other, with the ankle portion having an upwardly extending attachment section providing ease of manufacture and resistance to rotation, whereby both the foot portion and the ankle portion can be readily exchanged with correspondingly constructed foot and ankle portions to provide size adjustment or accommodation of different spring rates to suit the size of foot of the amputee or the stride and weight of the amputee, and further adjustments can be made by the use of an auxiliary ankle spring member. Therefore, an almost infinite combination of spring rate and size can be provided to the amputee, achieving a natural stride and resilience of gait, which has not been obtainable by prior art prosthetic devices.
Another object of the invention is the provision in a prosthetic foot of the aforementioned character of an interchangeable or permanent foot portion which has a toe section, an arch section, and a heel section, all constructed without the necessity of tapering of the thickness thereof. Also incorporated in the aforementioned foot is an ankle portion which incorporates an upper attachment section, a curvilinear ankle section, and a lower attachment section secured to the intersection of the arch and toe sections of the foot portion. The previously mentioned heel section of the foot portion extends beyond the curvilinear ankle and attachment sections of the ankle portion.
As previously indicated, the ankle portion can be provided in different sizes and spring rates, and an auxiliary ankle member may be utilized, thus permitting the gait, weight, and activity level of the amputee to be readily accommodated. Correspondingly, the ankle portion can be demountably associated with the foot portion of the foot to permit different sizes of foot portion having different spring rates to be mounted in operative relationship with the ankle portion.
Another object of the invention is the provision of a prosthetic foot of the aforementioned character in which both the foot and ankle portions of the foot are fabricated, and the auxiliary ankle may be fabricated, from superimposed laminates maintained in operative relationship by an encapsulating polymer, and further in which said toe, arch and heel sections of said foot portion, said spring section of said ankle portion, and said auxiliary ankle attachment are susceptible to bending stress determined by the number of the laminates and polymers in the respective toe, arch and heel sections of said foot portion, in said spring section of said ankle portion, and in said auxiliary ankle attachment. Thus, the various portions and sections thereof are encapsulated in a polymer and capable of spring stress response as ankle loads are imposed thereupon during the utilization of said foot.
A further object of the invention is the provision, in a prosthetic foot of the aforementioned character, of a foot portion which consists of continuous, integrally and simultaneously formed toe, arch, and heel sections, said sections being fabricated as a unitary structure by polymer impregnation of superimposed reinforcing laminae maintained in the desired configuration of said foot portion and said toe, arch and heel sections being capable of spring stress generated energy storage whereby the subjection of the toe or heel sections to bending moments will cause uniform transmission of spring stress through said arch section and through said curvilinear ankle section of said ankle portion to said attachment section thereof.
Another object of the invention is the provision of the aforesaid prosthetic foot in which the ankle section of said ankle portion has its upper extremity constituted by said upper attachment section and its lower extremity extending into and constituting said lower attachment section, said lower extremity, said curvilinear ankle section and said upper attachment section maintaining an approximately uniform thickness transversely of the longitudinal axis of said sections. Similarly, said foot portion and its various sections are provided with an approximately uniform thickness transversely of the longitudinal axis of said sections.
A further object of the invention is the provision of the aforesaid auxiliary ankle attachment, which is associated with the ankle section of said ankle portion to increase the resistance of said ankle section to loads imposed upon the toe section of said foot portion. The concept of the auxiliary ankle involves the provision of ankle members characterized by different spring rates, which permits the resistance of the ankle section to deflection to be precisely adjusted to the weight, activity level and other characteristics of the individual for whom said foot is being adjusted.
The polymers utilized to encapsulate the fibrous laminae are characterized by elasticity and flexibility so that the foot and ankle portions deflect proportionally to the engagement of said foot portion with an adjacent surface, causing the resultant energy to be stored and subsequently released when the gait of the amputee incorporating thrust and lift components results in the utilization of the stored energy and a consequent reduction of the energy expended by the amputee. There is a gradual increase in stiffness as the lever arm of the toe section of the foot portion shortens due to gradual deflection thereof.
It is an additional object of my invention to provide an improved coupling mechanism for attaching a prosthetic foot of the abovementioned character to an auxiliary pylon tube which is in turn attached to the wearer""s leg.
Another object of the invention is the provision in a prosthetic foot of the aforementioned character of a forefoot portion which incorporates an upwardly extending attachment section, a curvilinear ankle section, an arch section and a toe section. As previously mentioned, the forefoot portion can be provided in different sizes and spring rates, and an auxiliary ankle member may be utilized, thus permitting the gait, weight, and size of foot of the amputee to be readily accommodated. Also incorporated in the aforementioned foot is an interchangeable or permanent heel portion which has an attachment section secured to the intersection of the arch and toe sections of the forefoot portion and a heel section extending beyond the curvilinear ankle and attachment sections of the forefoot portion.
In order to impart a cosmetic aspect to the prosthetic foot, after proper fitting of the foot to insure that the foot and ankle portions and the auxiliary ankle are properly balanced and of appropriate size, the prosthesis may be encapsulated in a suitably shaped foot-like shroud to facilitate the utilization of the prosthetic foot with a conventional shoe. The enclosure must be sufficiently flexible so as not to inhibit the free movement and flexure of the foot and ankle portions and the auxiliary ankle of the prosthetic foot, but, because of the inherently resilient and stress-absorbing characteristics of said foot, little dependence is needed upon the ancillary cushioning action of the enclosure.
Consequently, the foot of my invention is characterized by extreme light weight, instantaneous response to imposed loads and correspondingly instantaneous delivery of stored energy when the gait of the wearer indicates that such stored energy is to be released. Moreover, the foot may be readily mounted in operative relationship with conventional ancillary pylons and couplings, and can be fine-tuned by the blending of the foot and ankle portions and auxiliary ankle characteristics to achieve the ultimate in operative response to the needs of the wearer.
Consequently, the wearer of the foot may engage in a wide variety of activities which were precluded in the past because of the structural limitations and corresponding performances of prior art prostheses. Running, jumping and other activities are sustained by the foot and it may be utilized in the same manner as the normal foot of the wearer.